On Tue, 24 Oct 2006 16:50:40 GMT, You wrote:

In article ,
legg wrote:

A properly designed crowbar should be able to handle the current and
stored charge of the supply it's monitoring. If a crowbar fails short
in the process, it's still doing it's job, but that is unlikely to
happen if foldback limiting occurs.

Actually, a Crowbar System ONLY needs to be able to blow the fuse,
or circuitbreaker that protects the LOAD from the overvoltage
condition that the Crowbar is monitoring. Protecting the supply
from overcurrent draw condition is the Foldback Current Limiter's
Job. Two completely different senerios.

The aim is to protect downstream components from overvoltage.
Overvoltage is an indication of loss of control. To count on the
presence of other limiting circuitry, completely independent of the
voltage regulator, may be whistlng for it.

At one time, thyristors with large I^2t characteristics were marketed
for crowbar applications. Nowadays, it might be more sensible to make
use of a semiconductor circuit breaker, integrated into bus sequencing
circuitry.

RL